U.S. patent number 11,201,077 [Application Number 16/621,432] was granted by the patent office on 2021-12-14 for parallel assembly of discrete components onto a substrate.
This patent grant is currently assigned to KULICKE & SOFFA NETHERLANDS B.V.. The grantee listed for this patent is KULICKE & SOFFA NETHERLANDS B.V.. Invention is credited to Ronn Kliger, Val Marinov, Matthew R. Semler.
United States Patent |
11,201,077 |
Marinov , et al. |
December 14, 2021 |
Parallel assembly of discrete components onto a substrate
Abstract
A method includes transferring multiple discrete components from
a first substrate to a second substrate, including illuminating
multiple regions on a top surface of a dynamic release layer, the
dynamic release layer adhering the multiple discrete components to
the first substrate, each of the irradiated regions being aligned
with a corresponding one of the discrete components. The
illuminating induces a plastic deformation in each of the
irradiated regions of the dynamic release layer. The plastic
deformation causes at least some of the discrete components to be
concurrently released from the first substrate.
Inventors: |
Marinov; Val (Fargo, ND),
Kliger; Ronn (Cambridge, MA), Semler; Matthew R. (Fargo,
ND) |
Applicant: |
Name |
City |
State |
Country |
Type |
KULICKE & SOFFA NETHERLANDS B.V. |
Eindhoven |
N/A |
NL |
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Assignee: |
KULICKE & SOFFA NETHERLANDS
B.V. (N/A)
|
Family
ID: |
1000005995112 |
Appl.
No.: |
16/621,432 |
Filed: |
April 25, 2018 |
PCT
Filed: |
April 25, 2018 |
PCT No.: |
PCT/US2018/029347 |
371(c)(1),(2),(4) Date: |
December 11, 2019 |
PCT
Pub. No.: |
WO2018/231344 |
PCT
Pub. Date: |
December 20, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200168498 A1 |
May 28, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62518270 |
Jun 12, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/6836 (20130101); B23K 26/354 (20151001); B23K
26/36 (20130101); H01L 25/0753 (20130101); H01L
33/62 (20130101); H01L 21/67115 (20130101); B23K
26/0673 (20130101); H01L 2221/68381 (20130101); G02B
27/1086 (20130101); H01L 33/0095 (20130101); H01L
2221/68363 (20130101); H01L 2933/0066 (20130101); H01L
33/50 (20130101); H01L 2221/68327 (20130101) |
Current International
Class: |
H01L
21/683 (20060101); B23K 26/354 (20140101); B23K
26/067 (20060101); H01L 33/62 (20100101); H01L
25/075 (20060101); B23K 26/36 (20140101); H01L
21/67 (20060101); H01L 33/00 (20100101); G02B
27/10 (20060101); H01L 33/50 (20100101) |
Field of
Search: |
;438/28 |
References Cited
[Referenced By]
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Other References
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Application No. PCT/US2018/29347, dated Aug. 31, 2018, 17 pages.
cited by applicant .
Invitation to Pay Additional Fees in International Application No.
PCT/US2018/29347, dated Apr. 25, 2018, 2 pages. cited by applicant
.
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2018-553154, dated Dec. 9, 2019, 14 pages with English Translation.
cited by applicant .
Taiwanese Office Action in Taiwanese Application No. 107120190,
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applicant .
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Dec. 17, 2020, 14 pages. cited by applicant .
Korean Office Action in Korean Application No. 10-2018-7032338,
dated Feb. 5, 2020, 33 pages with English translation. cited by
applicant .
International Preliminary Report on Patentability in International
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cited by applicant .
Korean Office Action in KR Appln. No. 10-2020-7027175, dated May 7,
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cited by applicant.
|
Primary Examiner: Vu; Vu A
Attorney, Agent or Firm: Fish & Richardson P.C.
Government Interests
This invention was made with Government support under grant number
1632387 awarded by the National Science Foundation. The Government
has certain rights in this invention.
Parent Case Text
CLAIM OF PRIORITY
This application claims priority to U.S. Patent Application Ser.
No. 62/518,270, filed on Jun. 12, 2017, the contents of which are
incorporated here by reference in their entirety.
Claims
What is claimed is:
1. An apparatus comprising: a substrate assembly, including: a
substrate, a dynamic release layer disposed on a surface of the
substrate, and multiple discrete components adhered to the
substrate by the dynamic release layer; and an optical system
including at least one optical element configured to separate a
laser beam from a source of laser energy into multiple beamlets,
each beamlet configured to illuminate a corresponding region on a
top surface of the dynamic release layer, wherein the optical
system has: (i) a first configuration in which the at least one
optical element is in the path of the laser beam between the source
of laser energy and the dynamic release layer, in which when the
optical system is in the first configuration, the optical element
separates the laser beam into the multiple beamlets; and (ii) a
second configuration in which the optical element is not in the
path of the laser beam between the source of laser energy and the
dynamic release layer, in which when the optical system is in the
second configuration, the laser beam is incident on the top surface
of the dynamic release layer at a location corresponding to a
location of one of the discrete components.
2. The apparatus of claim 1, in which the at least one optical
element is configured to separate the laser beam from the source
into an irradiation pattern including the multiple beamlets, each
beamlet of the irradiation pattern configured to illuminate a
particular location on a given discrete component.
3. The apparatus of claim 2, in which the irradiation pattern
comprises multiple groups, and in which the optical system
comprises: a first optical element configured to separate the laser
beam from the source into the irradiation pattern; and a second
optical element configured to separate the irradiation pattern into
an output including multiple groups, each group having the
irradiation pattern.
4. The apparatus of claim 3, in which the first and second optical
elements each comprise a diffractive optical element.
5. The apparatus of claim 2, in which the irradiation pattern
comprises multiple beamlets, and in which the optical system
comprises: a first optical element configured to separate the laser
beam from the source into the multiple beamlets; and a second
optical element configured to separate each of the multiple
beamlets into an output having the irradiation pattern.
6. The apparatus of claim 1, comprising a scanning mechanism
configured to scan the output of the optical system to multiple
regions of the dynamic release layer, each region of the dynamic
release layer adhering a subset of the multiple discrete components
to the substrate.
7. The apparatus of claim 1, comprising a controller configured to
control an alignment of the laser beam with the location of one of
the discrete components based on information indicative of one or
more of a characteristic and a quality of each of one or more of
the discrete components.
8. The apparatus of claim 1, in which the optical system comprises:
a first optical element configured to separate the laser beam into
a first number of beamlets; a second optical element configured to
separate the laser beam into a second number of beamlets; and a
switching mechanism configured to position the first optical
element or the second optical element in the path of the laser
beam.
9. The apparatus of claim 1, in which one or more of a wavelength
and fluence of each beamlet of the laser energy is sufficient to
induce an ablation of at least a partial thickness of the dynamic
release layer in each of the irradiated regions, the ablation of
the partial thickness inducing a deformation in each of the
irradiated regions.
10. The apparatus of claim 1, in which an adhesion of the dynamic
release layer is responsive to a stimulus.
11. The apparatus of claim 1, in which the discrete components
comprise LEDs.
12. An apparatus comprising: a substrate assembly, including: a
substrate, a dynamic release layer disposed on a surface of the
substrate, and multiple discrete components adhered to the
substrate by the dynamic release layer; and an optical system
including at least one optical element configured to separate a
laser beam from a source of laser energy into multiple beamlets,
each beamlet configured to illuminate a corresponding region on a
top surface of the dynamic release layer, wherein the optical
system includes: a first optical element configured to separate the
laser beam into a first number of beamlets; a second optical
element configured to separate the laser beam into a second number
of beamlets; and a switching mechanism configured to position the
first optical element or the second optical element in the path of
the laser beam.
13. The apparatus of claim 12, in which the at least one optical
element is configured to separate the laser beam from the source
into an irradiation pattern including the multiple beamlets, each
beamlet of the irradiation pattern configured to illuminate a
particular location on a given discrete component.
14. The apparatus of claim 13, in which the irradiation pattern
comprises multiple groups, and in which the optical system
comprises: a first optical element configured to separate the laser
beam from the source into the irradiation pattern; and a second
optical element configured to separate the irradiation pattern into
an output including multiple groups, each group having the
irradiation pattern.
15. The apparatus of claim 14, in which the first and second
optical elements each comprise a diffractive optical element.
16. The apparatus of claim 13, in which the irradiation pattern
comprises multiple beamlets, and in which the optical system
comprises: a first optical element configured to separate the laser
beam from the source into the multiple beamlets; and a second
optical element configured to separate each of the multiple
beamlets into an output having the irradiation pattern.
17. The apparatus of claim 12, comprising a scanning mechanism
configured to scan the output of the optical system to multiple
regions of the dynamic release layer, each region of the dynamic
release layer adhering a subset of the multiple discrete components
to the substrate.
18. The apparatus of claim 12, in which the optical system has: (i)
a first configuration in which the at least one optical element is
in the path of the laser beam between the source of laser energy
and the dynamic release layer, in which when the optical system is
in the first configuration, the optical element separates the laser
beam into the multiple beamlets; and (ii) a second configuration in
which the optical element is not in the path of the laser beam
between the source of laser energy and the dynamic release layer,
in which when the optical system is in the second configuration,
the laser beam is incident on the top surface of the dynamic
release layer at a location corresponding to a location of one of
the discrete components.
19. The apparatus of claim 18, comprising a controller configured
to control an alignment of the laser beam with the location of one
of the discrete components based on information indicative of one
or more of a characteristic and a quality of each of one or more of
the discrete components.
20. The apparatus of claim 12, in which one or more of a wavelength
and fluence of each beamlet of the laser energy is sufficient to
induce an ablation of at least a partial thickness of the dynamic
release layer in each of the irradiated regions, the ablation of
the partial thickness inducing a deformation in each of the
irradiated regions.
21. The apparatus of claim 12, in which an adhesion of the dynamic
release layer is responsive to a stimulus.
22. The apparatus of claim 12, in which the discrete components
comprise LEDs.
Description
BACKGROUND
This description relates generally to assembling discrete
components onto a substrate.
SUMMARY
In an aspect, a method includes transferring multiple discrete
components from a first substrate to a second substrate, including
concurrently irradiating multiple regions on a top surface of a
dynamic release layer, the dynamic release layer adhering the
multiple discrete components to the first substrate, each of the
irradiated regions being aligned with a corresponding one of the
discrete components. The irradiating induces an ablation of at
least a portion of the dynamic release layer in each of the
irradiated regions. The ablation causes at least some of the
discrete components to be concurrently released from the first
substrate.
Embodiments can include one or more of the following features.
Irradiating the multiple regions includes irradiating the multiple
regions with laser energy. The method includes separating the laser
energy into multiple beamlets, and irradiating each of the multiple
regions with one of the beamlets of laser energy. The method
includes separating the laser energy with a diffractive optical
element. The irradiating induces ablation of a partial thickness of
the dynamic release layer in each of the irradiated regions. The
ablation of the partial thickness of the dynamic release layer
induces a deformation of a remaining thickness of the dynamic
release layer in each of the irradiated regions. The deformation
includes a blister in each of the irradiated regions of the dynamic
release layer, the blisters each exerting a force on the
corresponding discrete component. The force exerted by the blisters
causes the discrete components to be released from the first
substrate. The ablation of the partial thickness induces a plastic
deformation in each of the irradiated regions. The ablation of the
partial thickness induces an elastic deformation in each of the
irradiated regions. The irradiating induces ablation of an entire
thickness of the dynamic release layer in each of the irradiated
regions. The method includes reducing an adhesion of the dynamic
release layer prior to irradiating the multiple regions. Reducing
an adhesion of the dynamic release layer includes exposing the
dynamic release layer to a stimulus. Exposing the dynamic release
layer to a stimulus includes exposing the dynamic release layer to
one or more of heat and ultraviolet light. Transferring the
multiple discrete components includes transferring a first set of
one or more discrete components to a first target substrate, the
discrete components in the first set sharing a first common
characteristic; and transferring a second set of one or more
discrete components to a second target substrate, the discrete
components in the second set sharing a second common
characteristic. The discrete components include light emitting
diodes (LEDs), and in which the characteristic includes one or more
of an optical characteristic and an electrical characteristic.
Transferring the multiple discrete components to the second
substrate includes transferring fewer than all of the discrete
components from the first substrate to the second substrate. The
method includes, before transferring the multiple discrete
components, transferring each of one or more of the discrete
components individually from the first substrate to a destination.
Transferring each of one or more of the discrete components
individually includes transferring the discrete components that do
not satisfy a quality criterion. The method includes, after
transferring the multiple discrete components to the second
substrate, transferring each of one or more discrete components
that remain on the first substrate individually to the second
substrate. The method includes, after transferring the multiple
discrete components to the second substrate, transferring each of
one or more discrete components from a third substrate individually
to the second substrate. The multiple discrete components form an
array of discrete components on the second substrate, and in which
transferring each of one or more discrete components that remain on
the first substrate includes transferring a discrete component to
an empty position in the array on the second substrate. Irradiating
multiple regions includes scanning the irradiation to multiple
subsets of discrete components. The multiple discrete components in
each subset are released concurrently, and the multiple subsets are
released successively. Irradiating multiple regions includes
irradiating each region with an irradiation pattern. The method
includes separating laser energy into the irradiation pattern. The
method includes separating the laser energy into the irradiation
pattern with a first diffractive optical element. The method
includes separating the irradiation pattern into multiple beamlets
of laser energy, each beamlet having the irradiation pattern. The
method includes separating the irradiation pattern into multiple
beamlets with a second diffractive optical element. The method
includes scanning the multiple beamlets of laser energy, each
having the irradiation pattern, to multiple subsets of discrete
components. The method includes separating laser energy into
multiple beamlets of laser energy, each beamlet having the
irradiation pattern, with a single diffractive optical element. The
irradiation pattern includes multiple beamlets of laser energy,
each beamlet corresponding to a particular location on a given
discrete component. The irradiation pattern includes four beamlets
of laser energy, each beamlet corresponding to a corner of a given
discrete component. Transferring the multiple discrete components
from the first substrate to the second substrate includes
transferring the multiple discrete components to the second
substrate in a face-down orientation. The multiple discrete
components include light emitting diodes (LEDs).
In an aspect, an apparatus includes a substrate assembly, including
a substrate, a dynamic release layer disposed on a surface of the
substrate, and multiple discrete components adhered to the
substrate by the dynamic release layer; and an optical system
including at least one optical element configured to separate a
laser beam from a source of laser energy into multiple beamlets,
each beamlet configured to illuminate a corresponding region on a
top surface of the dynamic release layer.
Embodiments can include one or more of the following features.
The at least one optical element is configured to separate the
laser beam from the source into the multiple beamlets, each beamlet
having an irradiation pattern. The irradiation pattern includes
multiple beamlets of laser energy, each beamlet of the irradiation
pattern configured to illuminate a particular location on a given
discrete component. The optical system includes a first optical
element configured to separate the laser beam from the source into
the irradiation pattern; and a second optical element configured to
separate the irradiation pattern into the multiple beamlets, each
beamlet having the irradiation pattern. The first and second
optical elements each include a diffractive optical element. The
optical system includes a first optical element configured to
separate the laser beam from the source into the multiple beamlets;
and a second optical element configured to separate each of the
multiple beamlets into the irradiation pattern. The apparatus
includes a scanning mechanism configured to scan the multiple
beamlets of laser energy to multiple regions of the dynamic release
layer, each region of the dynamic release layer adhering a subset
of the multiple discrete components to the substrate. The optical
system has (i) a first configuration in which the optical element
is in the path of the laser beam between the source of laser energy
and the dynamic release layer and (ii) a second configuration in
which the optical element is not in the path of the laser beam
between the source of laser energy and the dynamic release layer.
When the optical system is in the first configuration, the optical
element separates the laser beam into the multiple beamlets. When
the optical system is in the second configuration, the laser beam
is incident on the top surface of the dynamic release layer at a
location corresponding to a location of one of the discrete
components. The apparatus includes a controller configured to
control the alignment of the laser beam with the location of the
one of the discrete components. The controller is configured to
control the alignment of the laser beam based on information
indicative of one or more of a characteristic and a quality of each
of one or more of the discrete components. The optical system
includes a first optical element configured to separate the laser
beam into a first number ofbeamlets; a second optical element
configured to separate the laser beam into a second number of
beamlets; and a switching mechanism configured to position the
first optical element or the second optical element in the path of
the laser beam. The apparatus includes the source of laser energy.
The source of laser energy includes a laser. The irradiation of the
regions of the dynamic release layer causes release of the discrete
components aligned with the irradiated regions. One or more of a
wavelength and fluence of each beamlet of the laser energy is
sufficient to induce an ablation of at least a partial thickness of
the dynamic release layer in each of the irradiated regions. The
wavelength or fluence of each beamlet is sufficient to induce an
ablation of a partial thickness of the dynamic release layer in
each of the irradiated regions, the ablation of the partial
thickness inducing a deformation in each of the irradiated regions.
The wavelength or fluence of each beamlet is sufficient to induce
an ablation of an entire thickness of the dynamic release layer in
each of the irradiated regions. An adhesion of the dynamic release
layer is responsive to a stimulus. The adhesion of the dynamic
release layer is responsive to one or more of heat and ultraviolet
light. The discrete components include LEDs.
In an aspect, an apparatus includes a source of laser energy; a
substrate holder configured to receive a substrate; an optical
system including a first optical element configured to separate a
laser beam from the source of laser energy into multiple beamlets,
in which the optical system has a first configuration in which the
first optical element is disposed in the path of laser energy
between the source of laser energy and the substrate holder and at
least one second configuration, the at least one second
configuration being one or more of (i) a configuration in which a
second optical element is disposed in the path of the laser energy
and (ii) a configuration in which neither the first optical element
nor the second optical element is in the path of laser energy; and
a controller configured to control the configuration of the optical
system.
Embodiments can include one or more of the following features.
The apparatus includes a scanning device configured to scan the
laser beam or beamlets output from the optical system relative to
the substrate holder. The controller is configured to move the
first optical element into and out of the path of the laser energy.
The apparatus includes a stimulus application device configured to
output a stimulus including one or more of ultraviolet light and
heat. When a substrate is present in the substrate holder, the
stimulus application device is positioned to apply the stimulus to
the substrate.
In an aspect, an apparatus includes a source of laser energy; a
first substrate holder configured to receive at least one first
substrate; an optical system including a first optical element
configured to separate a laser beam from the source of laser energy
into multiple beamlets, in which the optical system has a first
configuration in which the first optical element is disposed in the
path of laser energy between the source of laser energy and the
first substrate holder and at least one second configuration, the
at least one second configuration being one or more of (i) a
configuration in which a second optical element is disposed in the
path of the laser energy and (ii) a configuration in which neither
the first optical element nor the second optical element is in the
path of laser energy; a first controller configured to control the
configuration of the optical system; a second substrate holder
configured to hold at least one second substrate, at least a
portion of the second substrate holder being disposed below the
first substrate holder; and a second controller configured to
control the positioning of the second substrate holder relative to
the first substrate holder. The apparatus includes a scanning
device configured to scan the laser beam or beamlets output from
the optical system relative to the substrate holder. The apparatus
includes a stimulus application device configured to output a
stimulus including one or more of ultraviolet light and heat. The
apparatus includes a control system, the control system including
the first controller and the second controller. The second
substrate holder is configured to hold multiple second substrates.
The apparatus includes a substrate rack configured to hold multiple
second substrates; and a transfer mechanism controllable by the
second controller to transfer one of the multiple second substrates
from the substrate rack to the second substrate holder. The first
substrate holder is configured to hold multiple first substrates.
The apparatus includes a substrate rack configured to hold multiple
first substrates; and a transfer mechanism controllable by a third
controller to transfer one of the multiple first substrates from
the substrate rack to the first substrate holder.
In an aspect, a method includes transferring multiple discrete
components from a substrate, the discrete components being adhered
to the substrate by a dynamic release layer, the transferring
including individually transferring each of one or more first
discrete components from the substrate to a first destination using
a first laser-assisted transfer process, the first discrete
components not satisfying a quality criterion; and transferring
multiple second discrete components from the substrate to a second
destination using a second laser-assisted transfer process, the
second discrete components satisfying the quality criterion.
Embodiments can include one or more of the following features.
Transferring multiple second discrete components includes
transferring fewer than all of the second discrete components such
that one or more second discrete components remain adhered to the
substrate. The method includes individually transferring each of
one or more of the second discrete components that remain adhered
to the substrate to the second destination. The multiple second
discrete components form an array of discrete components at the
second destination, and in which individually transferring each of
one or more of the second discrete components that remain includes
transferring each of the remaining second discrete components to an
empty position in the array. The second laser-assisted transfer
process includes irradiating multiple regions on a top surface of
the dynamic release layer, each of the irradiated regions being
aligned with a corresponding one of the second discrete components,
in which the irradiation causes the second discrete components to
be concurrently released from the substrate. The first
laser-assisted transfer process includes, for each of the first
discrete components irradiating a region on a top surface of the
dynamic release layer, the region being aligned with the first
discrete component, in which the irradiation causes the first
discrete component to be released from the substrate. The method
includes reducing an adhesion of the dynamic release layer prior to
transferring the one or more first discrete components. Reducing an
adhesion of the dynamic release layer includes exposing the dynamic
release layer to one or more of heat and ultraviolet light. The
second destination includes a target substrate, and in which
transferring the multiple second discrete components to the second
destination includes transferring the second discrete components
set onto an attachment element disposed on a top surface of the
target substrate. The method includes curing the attachment element
to bond the transferred second discrete components to the target
substrate. Curing the attachment element includes exposing the
attachment element to one or more of heat, ultraviolet light, and
mechanical pressure. The method includes applying the attachment
element to the target substrate. The second destination includes a
target substrate, and including bonding the transferred second
discrete components to the target substrate. The second destination
includes a target substrate having circuit components, and in which
the method includes interconnecting circuit components of the
transferred second discrete components to the circuit components of
the target substrate. The method includes transferring the discrete
components from a donor substrate to the substrate. Transferring
the discrete components from the donor substrate to the substrate
includes contacting the dynamic release layer on the substrate to
the discrete components on the donor substrate. The method includes
singulating the discrete components on the donor substrate. The
donor substrate includes a dicing tape. The donor substrate
includes a wafer. The method includes applying the dynamic release
layer to the substrate.
In an aspect, a method includes transferring discrete components
from a carrier substrate to each of multiple target substrates, the
discrete components being adhered to the carrier substrate by a
dynamic release layer, the transferring including using a
laser-assisted transfer process, transferring a first set of the
discrete components to a first target substrate using a
laser-assisted transfer process, the discrete components in the
first set sharing a first characteristic; and using the
laser-assisted transfer process, transferring a second set of the
discrete components to a second target substrate, the discrete
components in the second set sharing a second characteristic
different from the first characteristic.
Embodiments can include one or more of the following features.
The method includes transferring the discrete components from
multiple carrier substrates to the multiple target substrates. The
method includes transferring the discrete components consecutively
from each of the multiple carrier substrates. The transferring
includes transferring discrete components from a first carrier
substrate to one or more of the target substrates in a transfer
system; removing the first carrier substrate from a transfer
position in the transfer system; placing a second carrier substrate
in the transfer position; and transferring discrete components from
the second carrier substrate to one or more of the target
substrates. The transferring includes transferring the first set of
discrete components to the first target substrate in a transfer
system; removing the first target substrate from a transfer
position in the transfer system; and placing the second target
substrate in the transfer position for transfer of the second set
of discrete components. The discrete components include LEDs, and
in which the first and second characteristics include one or more
of an optical characteristic and an electrical characteristic.
Transferring each set of the discrete components to the
corresponding target substrate includes transferring each of the
discrete components in the set individually to the target
substrate. Transferring each set of discrete components to the
corresponding target substrate includes concurrently transferring
some or all of the discrete components in the set to the target
substrate. Transferring a set of discrete components to the
corresponding target substrate includes transferring the discrete
components in the set onto a layer of die catching material
disposed on a top surface of the target substrate. The method
includes applying the die receiving material to each target
substrate. The method includes reducing an adhesion of the dynamic
release layer. Reducing an adhesion of the dynamic release layer
includes exposing the dynamic release layer to one or more of heat
and ultraviolet light. The method includes transferring the
discrete components from a donor substrate to the carrier
substrate. Transferring the discrete components from the donor
substrate to the carrier substrate includes contacting the dynamic
release layer on the carrier substrate to the discrete components
on the donor substrate. The donor substrate includes a dicing tape.
The donor substrate includes a wafer. The method includes applying
the dynamic release layer to the carrier substrate.
In an aspect, an apparatus includes a substrate, multiple pockets
being formed in a top surface of the substrate; spectrum shifting
material disposed in each of the multiple pockets, the spectrum
shifting material configured to emit light at one or more emission
wavelengths responsive to absorbing light at an excitation
wavelength; and a LED disposed in each of the multiple pockets,
each LED configured to emit light at the excitation wavelength,
each LED oriented such that light emitted from the micro-LED
illuminates the spectrum shifting material disposed in the
corresponding pocket.
Embodiments can include one or more of the following features.
The spectrum shifting material includes a first spectrum shifting
material configured to emit light at a first emission wavelength;
and a second spectrum shifting material configured to emit light at
a second emission wavelength. The first spectrum shifting material
is disposed in a first subset of the multiple pockets and the
second spectrum shifting material is disposed in a second subset of
the multiple pockets. The pockets are arranged in a two-dimensional
array, and in which the first spectrum shifting material is
disposed in pockets in first rows of the array and the second
spectrum shifting material is disposed in pockets in second rows of
the array. The spectrum shifting material includes a third spectrum
shifting material configured to emit light at a third emission
wavelength, and in which the first emission wavelength corresponds
to red light, the second emission wavelength corresponds to green
light, and the third emission wavelength corresponds to blue light.
The LEDs are oriented such that a light-emitting face of each LED
faces away from the top surface of the substrate. Each LED includes
contacts formed on a second face of the LED, the second face
opposite the light-emitting face. The apparatus includes electrical
connection lines in electrical contact with the contacts of the
LEDs. The substrate is transparent to light at the one or more
emission wavelengths. The substrate absorbs light at the excitation
wavelength. The apparatus includes a planarization layer formed on
the top surface of the substrate. The planarization layer is
transparent to the one or more emission wavelengths. The spectrum
shifting material includes one or more of phosphors, quantum dots,
and organic dye. The apparatus includes a display device. Each
pocket, the spectrum shifting material disposed therein, and the
corresponding LED corresponds to a sub-pixel of the display device.
The apparatus includes a solid state lighting device.
In an aspect, a method includes disposing spectrum shifting
material in each of multiple pockets formed in a top surface of a
substrate, the spectrum shifting material configured to emit light
at one or more emission wavelengths responsive to absorbing light
at an excitation wavelength; and assembling a LED into each of the
multiple pockets, each LED configured to emit light at the
excitation wavelength, each LED oriented such that light emitted
from the LED illuminates the spectrum shifting material disposed in
the corresponding pocket.
Embodiments can include one or more of the following features.
The method includes forming the multiple pockets in the top surface
of the substrate. The method includes forming the multiple pockets
by one or more of embossing and lithography. Disposing the spectrum
shifting material includes disposing a first spectrum shifting
material in a first subset of the multiple pockets, the first
spectrum shifting material configured to emit light at a first
emission wavelength; and disposing a second spectrum shifting
material in a second subset of the multiple pockets, the second
spectrum shifting material configured to emit light at a second
emission wavelength. Assembling a LED into each of the multiple
pockets includes assembling the LEDs such that a light-emitting
face of each micro-LED faces away from the top surface of the
substrate. Assembling a-LED into each of the multiple pockets
includes concurrently transferring multiple LEDs into corresponding
pockets. Concurrently transferring multiple LEDs includes
transferring the multiple LEDs by a massively parallel
laser-assisted transfer process. The method includes forming an
electrical connection to each LED. The method includes forming an
electrical connection to a contact on a second face of each LED,
the second face opposite a light-emitting face of each LED. The
method includes forming a planarization layer on the top surface of
the substrate.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1A and 1B are diagrams of a laser-assisted transfer
process.
FIGS. 2A-2C are diagrams of a laser-assisted transfer process.
FIG. 3 is a diagram of a laser-assisted transfer process.
FIG. 4 is a diagram of a laser-assisted transfer process.
FIGS. 5A-5C are diagrams of a good-die-only transfer process.
FIGS. 6A-6C are diagrams of a good-die-only transfer process.
FIG. 7 is a diagram of an apparatus.
FIG. 8 is a diagram of a component sorting process.
FIG. 9 is a flow chart.
FIG. 10 is a diagram of a laser-assisted transfer process.
FIGS. 11A and 11B are diagrams of a micro-light emitting diode
(LED) device.
DETAILED DESCRIPTION
We describe here an approach for the massively parallel
laser-assisted transfer of discrete components onto a target
substrate. This process can enable ultra-fast, high throughput,
low-cost assembly of large numbers of discrete components. For
instance, light emitting diodes (LEDs) can be rapidly placed onto
substrates, thus creating LED arrays for use in devices such as
displays or solid state lighting.
Referring to FIGS. 1A and 1B, a laser-assisted transfer process is
used for high-throughput, low-cost contactless assembly of discrete
components onto rigid or flexible substrates. The term discrete
component refers generally to, for example, any unit that is to
become part of a product or electronic device, for example,
electronic, electromechanical, photovoltaic, photonic, or
optoelectronic components, modules, or systems, for example any
semiconductor material having a circuit formed on a portion of the
semiconducting material. The discrete components can be ultra-thin,
meaning having a maximum thickness of 50 .mu.m or less, 40 .mu.m or
less, 30 .mu.m or less, 25 .mu.m or less, 20 .mu.m or less, 10
.mu.m or less, or 5 .mu.m or less. The discrete components can be
ultra-small, meaning having a maximum length or width dimension
less than or equal to 300 .mu.m per side, 100 .mu.m per side, 50
.mu.m per side, 20 .mu.m per side, or 5 .mu.m per side. The
discrete components can be both ultra-thin and ultra-small.
Referring specifically to FIG. 1A, a discrete component 12 is
adhered to a carrier substrate 16 by a dynamic release layer 22.
The term carrier substrate refers generally to, for example, any
material including one or more discrete components, for example, a
collection of discrete components assembled by a manufacturer, such
as a wafer including one or more semiconductor dies.
The discrete component 12 includes an active face 32, which
includes an integrated circuit device. In the example of FIGS. 1A
and 1B, the active face 32 of the discrete component 12 faces away
from the dynamic release layer 22; in some examples, the active
face 32 can face toward the dynamic release layer 22.
Referring also to FIG. 1B, in a blistering transfer process, the
energy of the laser beam 24 is applied to a back side 30 of the
carrier substrate 16. The carrier substrate 16 is transparent to
the wavelength of the laser energy. The laser energy 24 thus passes
through the carrier substrate 16 and is incident on an area of the
dynamic release layer 22, causing ablation of a partial thickness
of the dynamic release layer in the area on which the laser energy
24 is incident (which we refer to as the irradiated area). The
ablation generates confined gas, which expands and generates a
stress in the non-ablated remainder of the dynamic release layer
22. The stress causes the material of the dynamic release layer to
deform elastically, forming a blister 26. If the stress resulting
from the elastic deformation exceeds the yield strength of the
dynamic release layer material, the dynamic release layer deforms
plastically. The blister 26 exerts a mechanical force on the
discrete component 12. When the mechanical force exerted by the
blister 26 is sufficient to overcome the adhesion between the
discrete component 12 and the dynamic release layer 22, the
mechanical force exerted by the blister 26 (in combination with
gravity) propels the discrete component away from the carrier
substrate 16, e.g., for transfer to a target substrate 28.
In an ablative transfer process, the energy of the laser beam 24 is
applied to the back side 30 of the transparent carrier substrate,
as shown in FIG. 1B. The laser energy 24 incident on an area of the
dynamic release layer 22 causes ablation of the complete thickness
of the dynamic release layer 22 in the irradiated area, thereby
eliminating any adhesion between the discrete component 12 and the
carrier substrate 16. The gases generated by the ablation, in
combination with gravity, propel the discrete component 12 away
from the carrier substrate 16, e.g., for transfer to the target
substrate 28.
Further description of a laser-assisted transfer process by
blistering of the dynamic release layer can be found in U.S. Patent
Publication No. US2014/0238592, the contents of which are
incorporated here by reference in their entirety.
In some examples, a laser-assisted transfer process can be used to
transfer multiple discrete components concurrently or near
concurrently. We sometime use the term concurrently to mean
generally concurrently or near concurrently. This process,
sometimes referred to as massively parallel laser-assisted
transfer, can enable ultra-fast, high throughput transfer of
discrete components onto a target substrate.
Referring to FIG. 2A, multiple discrete components 112 are adhered
to a single carrier substrate 116 by a dynamic release layer 122.
The multiple discrete components 112 can be arranged in an array,
such as a one-dimensional array or a two-dimensional array. The
dynamic release layer 122 of FIG. 2A can include one or more
layers.
Referring also to FIG. 2B, the energy of the laser beam 124 is used
for concurrent laser-assisted transfer of the multiple discrete
components 112 onto a target substrate 128. The carrier substrate
116 is transparent to the wavelength of the laser beam 124. The
laser beam 124 is divided into multiple beamlets 140a, 140b, 140c
by an optical element 142, such as a diffractive optical element,
e.g., a beam splitter. By beamlet, we mean a beam of light, such as
a beam of light having a smaller size (e.g., diameter) than the
laser beam 124. Each of the multiple beamlets 140a, 140b, 140c is
incident concurrently with each of the other beamlets on a
corresponding region of the dynamic release layer 122 that is
aligned with one of the multiple discrete components 112. In a
blistering transfer, the laser energy of each of the multiple
beamlets 140a, 140b, 140c induces concurrent formation of a blister
126 at each of the regions of the dynamic release layer 122. The
concurrent formation of multiple blisters 126 causes all of the
discrete components 112 aligned with the irradiated regions of the
dynamic release layer 122 to separate concurrently from the dynamic
release layer 122, e.g., for transfer to the target substrate
128.
Referring to FIG. 2C, in some examples, an ablative transfer can be
used for concurrent laser-assisted transfer of the multiple
discrete components 112 onto the target substrate. In concurrent
ablative transfer, the laser energy of each of the beamlets 140a,
140b, 140c induces concurrent ablation through the entire thickness
of the dynamic release layer 122 in the irradiated regions, thereby
causing the discrete components 112 aligned with the irradiated
regions to separate concurrently from the dynamic release layer
122, e.g., for transfer to the target substrate 128.
In the example of FIG. 2B, the laser beam 124 is divided into three
beamlets to be incident on discrete components 112 arranged in a
one-dimensional array. In some examples, the laser beam 124 can be
divided into multiple beamlets to be incident on discrete
components arranged in a two-dimensional array. The laser beam 124
can be divided into a larger number of beamlets, such as 10
beamlets, 100 beamlets, 500 beamlets, 1000 beamlets, 5000 beamlets,
10,000 beamlets, or another number of beamlets. The number of
beamlets into which the laser beam 124 can be divided can be
dependent on the energy of the laser producing the laser beam 124.
The number of beamlets can be dependent on the size of the discrete
components 112 being transferred. For instance, larger discrete
components can be transferred using a greater amount of energy than
smaller discrete components, and thus the laser beam 124 can be
divided into fewer beamlets for transferring larger discrete
components than for transferring smaller discrete components.
In some examples, the laser beam 124 is divided into fewer beamlets
140 than the number of discrete components 112. The laser beam 124
can be scanned across the carrier substrate 116 to sequentially
transfer subsets of the multiple discrete components 112, where the
discrete components in each subset are transferred concurrently.
For instance, the laser beam 124 can be divided into a
two-dimensional pattern, e.g., to transfer a two-dimensional array
of discrete components, and the pattern can be scanned across the
carrier substrate to release two-dimensional arrays of discrete
components concurrently. In some examples, the pattern can vary for
different scan positions, e.g., to account for variations in the
type, size, or both of the discrete components on the carrier
substrate.
FIG. 3 shows a perspective view of a discrete component 112 and a
portion of a dynamic release layer 322 aligned with the discrete
component 112. The carrier substrate on which the dynamic release
layer 322 is adhered is not shown for simplicity. Laser beam 324 is
used to transfer the discrete component 112 onto a target
substrate. An optical element 342 divides the laser beam 324 into a
multi-beamlet pattern 326 that is incident on the dynamic release
layer aligned with the discrete component 112. Each beamlet pattern
causes either partial-thickness ablation of the dynamic release
layer and the formation of blisters, or through-thickness ablation
of the dynamic release layer, causing a force to be applied to the
discrete component at multiple positions. In the specific example
of FIG. 3, the multi-beamlet pattern 326 includes four beamlets
326a, 326b, 326c, 326d oriented such that the beamlets are incident
on the dynamic release layer aligned with the four corners of the
discrete component 112. This configuration causes a substantially
equivalent force to be applied to each corner of the discrete
component 112. The use of a multi-beamlet pattern of laser energy
to transfer a discrete component can help to achieve high yield and
precise placement of the discrete component onto the target
substrate.
FIG. 4 is a perspective view of multiple discrete components 112
and a dynamic release layer 422. The carrier substrate to which the
discrete components 112 are adhered is not shown for simplicity.
Laser beam 424 is used for concurrent transfer of the multiple
discrete components 112 onto a target substrate. The laser beam 424
is divided into a multi-beamlet pattern 426 by a first optical
element 428 of an optical system, such as a diffractive optical
element, e.g., a beam splitter. The multi-beamlet pattern 426
includes multiple beamlets in an arrangement to be incident on the
dynamic release layer aligned with a single discrete component. For
instance, the multi-beamlet pattern 426 can include four beamlets
of laser energy oriented to be incident on the dynamic release
layer aligned with the four corners of a discrete component.
The multi-beamlet pattern 426 undergoes a second split at a second
optical element 430 of the optical system, such as a diffractive
optical element, e.g., a beam splitter. The second split generates
multiple groups 432 of the multi-beamlet pattern 426 of laser
beams. Each group 432 is incident on a region of the dynamic
release layer that is aligned with one of the discrete components
112. The multiple beamlets within each group 432 cause multiple
blisters to form in the irradiated regions of the dynamic release
layer, or alternatively, cause through-thickness ablation to form
in the irradiated regions of the dynamic release layer. This
approach enables concurrent transfer of multiple discrete
components 112, while the use of multiple beamlets per discrete
component can help to achieve high yield and precise placement of
the discrete components onto the target substrate.
In the specific example of FIG. 4, the laser beam 424 is divided by
the first optical element 428 into a pattern 426 including four
beamlets, one beamlet for each corner of a discrete component. The
pattern 426 is divided by the second optical element 430 into three
groups 432a, 432b, 432d, each group including four beamlets of
laser energy. Each group 432 is incident on a region of the dynamic
release layer 422 that is aligned with a corresponding one of the
multiple discrete components 112, and within each group the four
beamlets are incident on the dynamic release layer aligned with the
four corners of the corresponding discrete component 112.
In the example of FIG. 4, the optical system includes two optical
elements 428, 430. In some examples, the optical system can include
a single optical element that divides the laser beam 424 into
multiple patterns, each pattern including multiple beamlets of
laser energy.
In some examples, the pattern 426 of laser beamlets is divided into
fewer groups 432 than the number of discrete components 112. The
set of groups 432 can be scanned across the carrier substrate (not
shown) to sequentially transfer subsets of the multiple discrete
components, where the discrete components in each subset are
transferred concurrently.
In examples in which the laser beam is scanned across the carrier
substrate, the energy density incident on the dynamic release layer
can change as the laser energy is scanned, e.g., due to variations
in the distance the laser energy travels from its source and the
angle at which the laser energy strikes the dynamic release layer.
Differences in energy density can affect the positional accuracy
with which the discrete components are transferred onto the target
substrate and the yield of the transfer process. In some examples,
the energy density (e.g., the laser fluence) can be adjusted to
compensate for variations in the angle at which the layer energy
strikes the dynamic release layer or variations in the distance
between the source of the laser energy and the points at which the
laser energy strikes the dynamic release layer. In some examples,
the energy density can be adjusted in accordance with changing the
pattern of beamlets, e.g., due to a change in a number of discrete
components to be transferred concurrently or due to a change in a
number of beamlets to be incident on a single discrete component.
In some examples, an optical element such as a lens, e.g., a
telecentric lens, can be used to reduce the variation in the angle
at which the laser energy strikes the dynamic release layer, thus
reducing differences in energy density. In some examples, the
output power of the laser can be adjusted based on the release
process, e.g., adjusted by scan position or by the pattern of
beamlets or by another aspect of the release process.
In some examples, the optical system is configured to be switched
between single-component mode in which a single discrete component
is individually transferred and a multiple-component mode in which
multiple discrete components are transferred concurrently. In an
example, the multiple discrete components 112 on the carrier
substrate may be discrete components from a wafer. Single-component
mode can be used to transfer one or more undesired discrete
components to a destination, such as a test substrate or a discard.
For instance, undesired discrete components can be discrete
components having circuitry that failed a test. Multiple-component
mode can then be used to transfer one or more of the remaining
discrete components to the target substrate.
In some examples, after the multiple-component mode transfer of one
or more of the remaining discrete components to the target
substrate, single-component mode can be used again to transfer
additional discrete components to positions on the target substrate
that are missing a discrete component (e.g., because the discrete
component at that position had been removed as undesirable, was
originally missing from a source substrate, or for another reason).
For instance, single-component mode can be used to transfer
discrete components that were not transferred during the
multiple-component transfer, e.g., discrete components from the
circumferential region of a wafer. The ability to transfer discrete
components in single-component mode can help increase yield, e.g.,
by enabling transfer of discrete components, such as components
near the edge of a wafer, that may be difficult to include in a
group of concurrently transferred discrete components.
In some examples, undesired discrete components can be identified
based on a wafer map indicating a characteristic of each of one or
more of the discrete components on the carrier substrate. In some
examples, the wafer map can be created based on testing before the
discrete components are adhered to the carrier substrate. For
instance, the wafer map can be created based on a testing of each
discrete component following manufacturing of the discrete
components, and the undesired discrete components can be those
components having circuitry that failed the post-manufacturing
test. Testing can include electrical testing of the circuitry of
the discrete component, optical testing of the optical output of an
LED discrete component, or other types of testing (e.g., testing of
the functionality of a sensor on the discrete component or the
operation of a microelectromechanical (MEMS) device on the discrete
component). In some examples, the wafer map can be created based on
in situ testing of the discrete components on the carrier
substrate. For instance, when the discrete components are
optoelectronic devices, a photoluminescence (PL) test can be
performed in which each discrete component is excited with low
power laser energy and the optical response after relaxation to
ground state is detected. The optical response can be used to
characterize the component.
FIGS. 5A-5C and 6A-6C show examples of this multiple-transfer
process, which we sometimes call a "good-die-only" transfer
process.
Referring specifically to FIG. 5A, discrete components 550 arranged
in an array are adhered to a carrier substrate 552 by a dynamic
release layer. A mapping indicates a characteristic of each of one
or more of the discrete components 550 in the array. For instance,
the mapping can be indicative of results of a post-manufacturing
test, a quality control test, or an in situ test, e.g., as
described above, and can indicate whether each discrete component
passed or failed the test. Discrete components that passed the test
(e.g., discrete components that satisfy a quality criterion) are
sometimes referred to as "good die" and discrete components that
failed the test (e.g., discrete components that do not satisfy the
quality criterion) are sometimes referred to as "bad die." In the
example mapping of FIG. 5A, bad die (e.g., the discrete component
550a) are shaded in dark gray and good die (e.g., the discrete
component 550b) are shaded in light gray. In a first transfer step,
the bad die are transferred in single-component mode to a
destination, such as a test substrate or a discard.
Referring to FIG. 5B, once the bad die have been transferred in the
single-component mode transfer, there is an empty position in the
array on the carrier substrate 552 where each bad die was
originally located. For instance, an empty position 554 in the
array corresponds to the location of the bad die 550a. At least a
portion of the remaining discrete components, which are the good
die, are transferred to a target substrate 556 in a second,
multiple-component transfer step, thus forming a second array of
transferred discrete components 550' on the target substrate.
A transfer field 558 can define on the carrier substrate 552 a
region of a desired size, a region encompassing a desired number
array positions, or a region encompassing a desired number of
discrete components. The multiple-component transfer process can
transfer only some or all of those discrete components that are
encompassed within the transfer field 558. Any discrete components
that are outside the transfer field 558 are not transferred to the
target substrate 556, and remain on the carrier substrate 552 as
remaining discrete components 560. In the example of FIG. 5B, the
transfer field 558 is sized to encompass a 10.times.10 array, and
the multiple-component transfer process transfers all of the
discrete components encompassed within the transfer field. The
array of transferred discrete components 550' on the target
substrate 556 is thus a 10.times.10 array of discrete components
(and empty positions, if any) in which the relative positioning of
discrete components and empty positions is preserved. The transfer
field can be sized based on a desired size or number of discrete
components for a downstream application, such as a light emitting
diode (LED) based display.
Referring to FIG. 5C, in some examples, the empty positions in the
array of transferred discrete components 550' on the target
substrate are filled in by a third transfer step. In the third
transfer step, each of one or more of the remaining discrete
components 560 (e.g., a remaining good discrete component) is
transferred in a single-component mode transfer process to one of
the empty positions (e.g., the empty position 554', see FIG. 5B) on
the target substrate 556. In some examples, the empty positions can
be filled in by transferring discrete components from a different
carrier substrate, e.g., if there are not enough discrete
components remaining on the carrier substrate 552 or if a different
type of discrete component is desired. At the completion of the
third transfer process, the array of transferred discrete
components 550' on the target substrate 556 is a complete array of
good discrete components with no empty positions.
Referring to FIGS. 6A-6C, in some examples, a good-die-only
transfer process transfers a specified pattern of discrete
components from the carrier substrate to the target substrate.
Referring specifically to FIG. 6A, discrete components 580 arranged
in an array are adhered to a carrier substrate 582 by a dynamic
release layer. A mapping of a characteristic of the discrete
components 580 indicates bad die (e.g., the discrete component
580a) in dark gray and good die (e.g., the discrete component 580b)
in light gray. In a first transfer step, the bad die are
transferred in single-component mode to a destination, such as a
test substrate or a discard.
Referring to FIG. 6B, once the bad die have been transferred in the
single-component mode transfer, there is an empty position in the
array on the carrier substrate 582 where each bad die was
originally located. A pattern of the remaining discrete components,
which are the good die, are transferred to a target substrate 586
in a second, multiple-component transfer step, thus forming a
second transferred array of transferred discrete components 580' on
the target substrate. For instance, a pattern of discrete
components encompassed within a transfer field 588 can be
transferred. In the example of FIG. 6B, the discrete components at
every other location in the array on the carrier substrate 582 is
transferred; if there is an empty position at one of these
locations, that empty position remains also in the transferred
array. Referring to FIG. 6C, in some examples, the empty positions
in the array of transferred discrete components 580' on the target
substrate are filled in by a third transfer step, e.g., by
transferring remaining discrete components from the carrier
substrate 582 or from another carrier substrate.
In some examples, the third transfer step is not executed and the
empty positions in the array of transferred discrete components
remain when the target substrate is provided to downstream
application. For instance, the third transfer step can be
eliminated if the density of discrete components in the array is
sufficient that a small number of empty positions will not
substantially affect the performance of the array in the downstream
application. In some examples, the third transfer step is optional
and can be carried out based on the array of transferred discrete
components satisfying (or not satisfying) a quality characteristic.
For instance, the third transfer step can be executed when there
are more than a threshold number or percentage of empty positions,
or when a threshold number of empty positions are adjacent to other
empty positions.
Referring to FIG. 7, the good-die-only process such as that shown
in FIGS. 5A-5C and 6A-6C can be carried out on a transfer apparatus
750 that is capable of switching between multiple-component mode
and single-component mode. For instance, the transfer apparatus 750
can include an automated optical element changer 752 that enables
various optical systems 754a, 754b, 754c to be moved into alignment
with a laser 753, e.g., depending on the type of transfer process
(e.g., multiple-component mode or single-component mode). In an
example, the optical system 754a can be a single-beam system and
the optical systems 754b, 754c can be multi-beam systems with
different beam configurations. Other configurations of optical
systems are also possible. In some examples, the transfer apparatus
750 can include multiple optical elements in the path of the laser
beam or beamlets, and the automated optical element changer 752 can
move one of the multiple optical elements into or out of the path.
The transfer apparatus can include a scanning mechanism (not shown)
that can scan the laser beam or beamlets output from each optical
system across the surface of a carrier substrate 758 to transfer
one or more discrete components 760.
The apparatus can be computer-controlled by one or more local or
remote computers or controllers 762 such that the end-to-end
multiple-transfer process can be automated. For instance, a
controller can control the alignment of the laser beam or beamlets
with each discrete component to be transferred in the first
single-component mode transfer. The controller can control the
alignment of the laser beam or beamlets with the discrete
components to be transferred in the second multi-component
transfer. The controller can control the alignment of the laser
beam or beamlets with each of the remaining discrete components to
be transferred in the single-component mode third transfer, and can
control the alignment of the carrier substrate with the target
substrate during the single-component mode third transfer. The
apparatus can include a stimulus application device 764 configured
to output a stimulus, such as ultraviolet light or heat, to be
applied to the carrier substrate, e.g., to reduce the adhesion of
the dynamic release layer.
The transfer apparatus can include a target substrate holder 766
for holding the target substrate. In some examples, the target
substrate holder 766 can hold multiple target substrates. In some
examples, such as in the example apparatus 750 of FIG. 7, the
target substrate holder 766 can hold a single target substrate 768'
in position to receive discrete components transferred from the
carrier substrate 758. A transfer rack 770 configured to hold one
or more target substrates 768 can be controlled by a controller 772
to move individual target substrates from the transfer rack 770 to
the target substrate holder 766. As an example, a first target
substrate can be held by the target substrate holder 766 to receive
a first transfer (e.g., bad die) from the carrier substrate 758. A
second target substrate can then be transferred from the transfer
rack 770 into the target substrate holder 766 to receive a second
transfer (e.g., good die) from the carrier substrate 758.
The transfer apparatus can include a carrier substrate holder 774
for holding the carrier substrate 758. In some examples, the
carrier substrate holder 774 can hold multiple carrier substrates.
In some examples, such as in the example apparatus 750 of FIG. 7,
the carrier substrate holder 774 can hold a single carrier
substrate. In some examples, a transfer rack (not shown) configured
to hold one or more carrier substrates can be controlled to move
individual substrates from the transfer rack to the carrier
substrate holder 774.
Referring to FIG. 8, in some examples, single-component mode or
multiple-component mode can be used to sort discrete components 600
held on a carrier substrate 602 by one or more characteristics of
the discrete components. For instance, when the discrete components
are LEDs, the characteristic can be an emission wavelength, quantum
output, a turn-on voltage, a light intensity, a voltage-current
characteristic, or another characteristic, or a combination of any
two or more of them. The characteristic can be indicated in a
mapping that indicates the characteristic for each of one or more
of the discrete components held on the carrier substrate 602. In
the sorting process, each set of discrete components that share a
common characteristic or combination of characteristics is
transferred to a corresponding target substrate, resulting in a set
of target substrates, each target substrate having a set of
discrete components that share a common characteristic (e.g., a
characteristic falling into a common range) or combination of
characteristics. The discrete components sharing a common
characteristic or combination of characteristics can be transferred
individually in single-component mode or concurrently in
multiple-component mode.
The transfer apparatus 750 of FIG. 7 can be used for sorting
discrete components by characteristics of the discrete components.
In some examples, the target substrate holder 766 can hold multiple
target substrates, and discrete components from a single carrier
substrate 758 can be transferred to respective target substrates
held in the target substrate holder 766 based on a characteristic
of the discrete components. In some examples, the target substrate
holder 766 can hold a single target substrate. A first set of
discrete components from the carrier substrate 758 sharing a common
characteristic or combination of characteristics can be transferred
to a first target substrate held in the target substrate holder
766. A second target substrate can then be transferred into the
target substrate holder 766 and a second set of discrete components
with a different common characteristic or combination of
characteristics can be transferred to the second target
substrate.
In the example of FIG. 8, discrete components 604 having a first
characteristic in common (e.g., LEDs having an emission wavelength
in a first range) are transferred from the carrier substrate 602 to
a first target substrate 606 in a first multiple-component mode
transfer. Discrete components 608 having a second characteristic in
common (e.g., LEDs having an emission wavelength in a second range)
are transferred from the carrier substrate 602 to a second target
substrate 610 in a second multiple-component mode transfer.
Discrete components 612 having a third characteristic in common
(e.g., LEDs having an emission wavelength in a third range) are
transferred from the carrier substrate 602 to a third target
substrate 614 in a third multiple-component mode transfer. Although
three target substrates are shown in FIG. 8, the sorting process
can transfer sets of discrete components to any number of target
substrates.
Referring to FIG. 9, in an example process for transferring
discrete components, singulated discrete components are provided on
a temporary substrate, such as a dicing tape; or on a donor
substrate such as a wafer, e.g., a silicon wafer or a sapphire
wafer (700). For instance, a wafer can be adhered to the dicing
tape and diced into the discrete components. Prior to adhering the
wafer to the dicing tape, the wafer can be thinned, e.g., to a
thickness of about 50 .mu.m. Further description of dicing a wafer
into discrete components is provided in PCT Application Serial No.
PCT/US2017/013216, filed Jan. 12, 2017, the contents of which are
incorporated here by reference in their entirety.
The singulated discrete components are transferred from the
temporary substrate to a transparent carrier substrate having a
dynamic release layer disposed thereon (702). In some examples, the
carrier substrate can be provided with the dynamic release layer
already applied. In some examples, the dynamic release layer is
applied to the carrier substrate. The carrier substrate is formed
of a material, such as glass or a transparent polymer, that is at
least partially transparent to at least some wavelengths of the
ultraviolet, visible, or infrared electromagnetic spectrum,
including the wavelength(s) to be used during the subsequent laser
assisted transfer process. In some examples, components of a
singulated wafer are transferred directly to the carrier substrate
without the use of a temporary substrate. For instance, direct
transfer of singulated components can be used to transfer epi-layer
thick micro-LEDs from a growth substrate to a carrier substrate
using a laser lift-off process.
In some examples, the singulated discrete components are
transferred to the carrier substrate in a good-die-only transfer
process in which "bad die" are first removed from the temporary
substrate and the remaining "good die" are then transferred to the
carrier substrate.
The discrete components are transferred from the temporary
substrate to the carrier substrate by contacting the discrete
components on the temporary substrate to the dynamic release layer
on the carrier substrate. In some examples, when the temporary
substrate is a dicing tape, the dicing tape can be formed of a
material that undergoes a reduction in adhesion responsive to a
stimulus, such as heat or ultraviolet light. When the dicing tape
is exposed to the stimulus, the adhesion of the dicing tape is
reduced, thereby facilitating the transfer of the discrete
components to the carrier substrate. Further description of
transferring discrete components onto a carrier substrate is
provided in PCT Application Serial No. PCT/US2017/013216, filed
Jan. 12, 2017, the contents of which are incorporated here by
reference in their entirety.
In some examples, the discrete components can be transferred to the
carrier substrate before dicing, e.g., as a whole or partial wafer.
For instance, the wafer or partial wafer can be mounted on the
carrier substrate and then the wafer can be diced into the discrete
components. In some examples, the wafer can be partially diced
prior to the transfer to the carrier substrate and the dicing can
be completed after the transfer to the carrier substrate.
In some examples, the dynamic release layer can be a material with
controllable adhesion, such as a material with an adhesion that can
be reduced upon exposure to a stimulus, such as heat, ultraviolet
light, or another stimulus. When the discrete components are
transferred to the carrier substrate, a highly adhesive dynamic
release layer facilitates the transfer and helps to secure the
discrete components on the carrier substrate. However, a less
adhesive dynamic release layer can facilitate a subsequent
laser-assisted transfer of the discrete components to a target
substrate. Accordingly, in some examples, once the discrete
components have been transferred to the carrier substrate, the
adhesion of the dynamic release layer is reduced (704), e.g., by
exposing the dynamic release layer to a stimulus such as heat or
ultraviolet light. Adhesion reduction causes reduced adhesion for
the entire dynamic release layer, and facilitates subsequent
laser-assisted transfer. Adhesion reduction is optional, as
indicated by the dashed line border in FIG. 8. For instance, in an
ablative laser-assisted transfer process, adhesion reduction is not
generally performed. Further description of dynamic release layers
having controllable adhesion is provided in PCT Application Serial
No. PCT/US2017/013216, filed Jan. 12, 2017, the contents of which
are incorporated here by reference in their entirety.
In some examples, in a sorting process, the discrete components are
transferred from the carrier substrate to multiple target
substrates in multiple laser-assisted transfer processes (706). For
instance, the discrete components can be transferred to target
substrates based on a characteristic of the discrete components,
thereby sorting the discrete components by that characteristic. The
outcome of the sorting process is a set of target substrates, each
target substrate having a set of discrete components that share a
common characteristic.
In some examples, each target substrate can have die catching
material disposed thereon. The die catching material (DCM) can be a
material that receives discrete components as they are transferred
from the carrier substrate and keeps them in their targeted
positions while reducing post-transfer movement of the discrete
components on the target substrate. The DCM can be selected based
on properties such as surface tension, viscosity, and rheology. For
instance, the DCM can provide viscous drag to prevent discrete
component movement, or can prevent discrete component movement by
another externally-applied force, such as an electrostatic force, a
magnetic force, a mechanical force, or a combination of any two or
more of them.
In some examples, the target substrates are provided with the die
catching material already applied. In some examples, the DCM is
applied to the target substrates prior to transfer of the discrete
components. DCM can be applied as a continuous film, e.g., with a
thickness of between about 3 .mu.m and about 20 .mu.m, using a film
deposition method such as spin coating, dip coating, wire coating,
doctor blade, or another film deposition method. Alternatively, DCM
can be applied as a discrete, patterned film, e.g., in the
locations at which discrete components are to be placed. A
patterned DCM film can be formed by material printing techniques
such as stencil printing, screen printing, jetting, inkjet
printing, or other techniques. A patterned DCM film can also be
formed by pre-treating the target substrate with a pattern of a
material that attracts the DCM, a material that repels the DCM, or
both, and then using a continuous film deposition method to deposit
the DCM, resulting in DCM in the regions with the DCM-attracting
material (or in the regions without the DCM repelling material).
For instance, the target substrate can be patterned with
hydrophilic material, hydrophobic material, or both.
In some examples, the discrete components on each target substrate
are transferred to a corresponding second substrate, such as a tape
(708). Because the discrete components were sorted by
characteristic during the transfer to the target substrate, each
tape will thus also receive discrete components sharing a common
characteristic. The tapes can be provided for downstream
applications, e.g., to end product manufacturers. The transfer of
the discrete components to the second substrate can be a contact
transfer. When the target substrates include a layer of die
catching material with controllable adhesion, the attachment
element can be exposed to a stimulus to reduce the adhesion,
thereby facilitating transfer of the discrete components.
In some examples, the discrete components are transferred to a
device substrate in a laser-assisted transfer process (710). The
transfer of the discrete components to the device substrate can
include a good-die-only transfer process as described above, in
which bad die are first transferred from the carrier substrate to a
discard, and an array of good die is then transferred concurrently
from the carrier substrate to the device substrate.
In some examples, the device substrate can have a conductive
attachment element disposed thereon to enable die catching and
interconnection. The attachment element cures responsive to an
applied stimulus, such as a material that is thermally curable,
curable upon exposure to ultraviolet light, or curable in response
to another type of stimulus, or a combination of any two or more of
them. In some examples, the device substrate is provided with the
attachment element already applied. In some examples, the
attachment element is applied to the target substrates prior to
transfer of the discrete components. In some examples, the device
substrate can have an attachment element disposed thereon that
serves as a flux during soldering, and the die catching material is
activated by heating to facilitate soldering as a process for
interconnection of the discrete components. Further description of
attachment elements is provided in PCT Application Serial No.
PCT/US2017/013216, filed Jan. 12, 2017, the contents of which are
incorporated here by reference in their entirety.
The discrete components are bonded to the device substrate (712).
For instance, the attachment element can be cured, e.g., by
exposure to a stimulus such as a high temperature, ultraviolet
light, or another stimulus, or a combination of any two or more of
them, thereby increasing the adhesion of the attachment element.
The stimulus can be removed after a time sufficient to allow the
attachment element to cure, thus forming a mechanical bond, an
electrical bond, or both, between the device substrate and the
discrete components. Further description of bonding discrete
components to a device substrate is provided in PCT Application
Serial No. PCT/US2017/013216, filed Jan. 12, 2017, the contents of
which are incorporated here by reference in their entirety.
The discrete components are interconnected to the device substrate
(714) to establish electrical connections between circuit elements
on the discrete components and circuit elements on the device
substrate. In some examples, the discrete components are
interconnected to the device substrate in a face-up orientation
with the active face of the discrete component facing away from the
device substrate. The active face of a discrete component is the
surface on which the circuitry of the discrete component is formed.
For face-up discrete components, interconnection can include wire
bonding, isoplanar printing (in which a conductive material is
printed onto the device substrate and the active face of the
discrete component), direct write material deposition, thin film
lithography, or other interconnection methods. In some examples,
the discrete components are interconnected to the device substrate
in a face-down orientation (sometimes referred to as "flip-chip")
with the active face of the discrete component facing toward the
device substrate. Flip-chip interconnection can include adhesive
bonding, soldering, thermocompression bonding, ultrasonic bonding,
or other flip-chip interconnection methods.
Referring to FIG. 10, in an example process 800 for transferring
discrete components, such as micro LEDs, singulated discrete
components are provided on a substrate (802), such as a wafer,
e.g., a sapphire wafer.
In some examples, the discrete components are transferred to an
intermediate substrate (804), e.g., by contacting the discrete
components on the donor substrate to the intermediate substrate.
For instance, an intermediate substrate can be used for cases in
which the discrete component is to be flipped (i.e., turned over
180.degree.) for an ultimate downstream application. An
intermediate substrate can also sometimes improve a metric
associated with the transfer process, such as yield, accuracy, or
another metric. The discrete components are then transferred from
the intermediate substrate to a transparent carrier substrate
having a dynamic release layer disposed thereon (806).
In some examples, the intermediate substrate is not used and the
discrete components are transferred directly from the donor
substrate to the transparent carrier substrate. In such cases, the
aspect 804 of the transfer process is skipped and the aspect 806 of
the transfer process is a transfer of the discrete components from
the donor substrate directly to the transparent carrier substrate.
The transfer of the discrete components from the substrate (e.g.,
the sapphire wafer) to either the intermediate substrate or the
carrier substrate can be performed by a laser liftoff process. In a
laser liftoff process, the active (functional) layers of a
component are separated from a substrate by changing the material
composition at an interfacial layer between the functional layers
and the substrate. For instance, in a laser liftoff process of GaN
micro-LEDs grown epitaxially on a sapphire substrate, a laser
(e.g., an ultraviolet laser) is focused on the interface between
the GaN layers of the micro-LEDs and the sapphire substrate. The
high temperature in the area on which the laser is focused causes
decomposition of a thin (e.g., less than 1 .mu.m thick) layer of
GaN into gallium and nitrogen. The melting point of gallium is very
low (about 30.degree. C.), thus enabling the functional GaN layers
of the micro-LEDs to be easily removed by melting the gallium
layer.
The adhesion of the dynamic release layer is reduced (808) by
application of a stimulus, such as heat, ultraviolet light, or
another type of stimulus. The discrete components are then
transferred using a laser-assisted transfer process to a device
substrate (810). In the example of FIG. 10, the discrete components
are shown as being transferred individually in single-component
mode. In some examples, multiple discrete components can be
transferred concurrently in multiple-component mode. In some
examples, the discrete component transfer includes the
good-die-only process in which bad die are removed from the carrier
substrate in a first transfer process and good die are then
transferred to the device substrate in a second transfer process.
The discrete components on the device substrate are bonded to the
device substrate and interconnected to circuit elements on the
device substrate (812).
The approaches described above for massively parallel
laser-assisted transfer of multiple discrete components can be used
to assemble micro-LEDs for use in micro-LED-based devices, such as
displays, e.g., television screens or computer monitors; or solid
state lighting. Micro-LED-based devices include an array of
micro-LEDs, each micro-LED forming an individual pixel or sub-pixel
element. In some examples, colors can be achieved by using
micro-LEDs that emit different wavelengths. In some examples,
colors can be achieved by using micro-LEDs in conjunction with
spectrum shifting materials such as organic dyes, phosphors,
quantum dots, or by using color filters.
By micro-LEDs, we mean LEDs having at least one lateral dimension
of at most 100 microns. By spectrum-shifting material, we mean a
material that is excited by light at a first wavelength (sometimes
referred to as an excitation wavelength) to emit light at a second
wavelength (sometimes referred to as an emission wavelength)
different from the excitation wavelength. When a spectrum shifting
material is implemented by color filters, the color of the spectrum
shifting material is the color that corresponds to the wavelength
of light emitted by the spectrum shifting material. When a spectrum
shifting material is implemented by quantum dots, the color of the
spectrum shifting material depends on the size of the quantum dots.
When a spectrum shifting material is implemented by organic dyes or
phosphors, the color of the spectrum shifting material depends on
the composition of the dye or phosphor.
Referring to FIGS. 11A and 11B, a micro-LED device 500 includes a
substrate 502 with an array of pockets 504 formed in a top surface
of the substrate 502. Each pocket 504 corresponds to a sub-pixel of
the device 500. The pockets 504 can be formed by embossing,
lithography, or another manufacturing method. Spectrum shifting
material 506 is disposed in at least some of the pockets 504. The
color of the spectrum shifting material 506 can vary across the
array of pockets 504, e.g., by row, by column, in another pattern,
or randomly. In the example of FIGS. 11A and 11B, the color of the
spectrum shifting material 506 varies by column of the array of
pockets 504, such that a first column 508a has red spectrum
shifting material in its pockets 504, a second column 508b has
green spectrum shifting material in its pockets 504, and a third
column 508c has blue spectrum shifting material in its pockets. The
substrate 502 can be made of a material that is transparent to the
colors of the spectrum shifting material. For instance, the
substrate 502 can be glass or a transparent polymer.
A micro-LED 510 is placed into each pocket 504 in the substrate
502. For instance, the micro-LEDs 510 can be placed into the
pockets 504 using the approaches described above for massively
parallel laser-assisted transfer of multiple discrete components.
The micro-LEDs 510 are placed in the pockets 504 with the spectrum
shifting material 506 encompassing the light-emitting surfaces and
side surfaces of the micro-LEDs 510. The micro-LEDs 510 emit light
of a wavelength that can excite the spectrum shifting material 506
to emit light. For instance, the micro-LEDs can emit ultraviolet
light.
In the example of FIGS. 11A and 11B, the micro-LEDs 510 are
controlled by a passive matrix in which electrical contacts 512 on
the opposite side of the micro-LEDs 510 are exposed toward a top
surface 514 of the substrate 502. Row and column electrodes 516,
518 are connected to the electrical contacts 512 of the micro-LEDs
510, providing a way to address each micro-LED 510 individually to
excite a given pixel or sub-pixel of spectrum shifting material
506. A planarization layer 520 is formed over the top surface 514.
The planarization layer 520 can be transparent or opaque to light
from the spectrum shifting material 506. In some examples, the
micro-LEDs are controlled by active matrix technology in which each
micro-LED is controlled individually using electronic components
such as thin film transistors and capacitors.
The transparent substrate is transparent to the light emitted by
the spectrum shifting materials but absorbs the light emitted by
the micro-LEDs. The planarization layer can be transparent or
opaque to the light emitted by the spectrum shifting material.
In some examples, the walls of the substrate 502 between the
pockets 504 absorb the light emitted by the micro-LEDs 510,
preventing the light from one micro-LED from exciting the spectrum
shifting material 506 in a different pocket 504 and thus reducing
or eliminating cross-talk and color pollution between neighboring
sub-pixels. The presence of the spectrum shifting material 506
encompassing the light-emitting surfaces and side surfaces of the
micro-LEDs 510 can also help to reduce or eliminate cross-talk and
color pollution. In some examples, the walls of the substrate 502
between the pockets 504 can be metallized to reduce or eliminate
cross-talk, to improve quantum efficiency by reflecting light that
may otherwise have been lost to absorption by the walls, and to
improve the directionality of the emitted light.
The micro-LEDs 510 can be assembled into the device 500 using the
approaches described above for massively parallel laser-assisted
transfer of multiple discrete components. Using these approaches,
the micro-LEDs 510 can be assembled quickly, enabling high
throughput fabrication. For instance, assembling micro-LEDs into a
full HD display using the approaches described above would take
less than about ten minutes, such as about 1 minute, about 2
minutes, about 4 minutes, about 6 minutes, about 8 minutes, or
about 10 minutes. In contrast, transferring each micro-LED
individually to assemble the same display using contemporary
conventional approaches would take one or more hours of magnitude
longer, such as about 100 hours, about 200 hours, about 400 hours,
about 600 hours, or about 800 hours.
In some examples, the approaches described here for concurrent
transfer of multiple discrete components can be used for assembly
of other devices, such as micro solar cells or
microelectromechanical (MEMS) devices. For instance, to assemble
components of MEMS mirrors, the pattern of the beamlets of laser
energy can be dynamically changed according to the specifications
of the mirror. Another example is the heterogeneous integration of
system-on-chip (SoC) or system-in-package (SiP) components, where a
large number of functional blocks (chiplets) need to be transferred
to an interposer substrate where they are aggregated together to
form the SoC/SiP component.
A number of embodiments of the invention have been described.
Nevertheless, it will be understood that various modifications may
be made without departing from the spirit and scope of the
invention. For example, some of the steps described above may be
order independent, and thus can be performed in an order different
from that described.
Other implementations are also within the scope of the following
claims.
* * * * *